Electromagnetic sound reproducer



April 13 1926.

- R. L. BROWN ELECTROMAGNETIC SOUND REPRODUCER Filed Nov. 28, 1925 FALPH 1. 5/?0W/Y INVENTOR.

M ATTORNEY Patented Apr. 13, 1926.

UNITED STATES PATENT on-ice.

RALPH L. BROWN, OF NEWARK, NEW ERSEY, ASSIGNOR T0 BRANDES LABORATORIES, INC., OF NEWARK, NEW JERSEY, A CORPORATION OF NEW JERSEY.

ELECTROMAGNETIC SOUND REPROD'UCER.

Application filed November 28,1925. Serial No. 71,977.

To all whom it may concern:

Be it known that I, RALRH L. BROWN, a citizen of the United States, residing at Newark, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in an Electromagnetic Sound Reproducer, of which the following is a specification.

My invention relates broadly to electromagnetic sound reproducers, and more particularly to the construction of a driver for an electromagnetic sound reproducer.

One of the objects of my invention is to provide a construction of driver for an electromagnetic sound reproducer, which may be used either as a phonograph unit or as an electromagnetic actuating system for a conical or other shaped diaphragm, where considerable power is necessary in reproducing mechanical vibrations from the electrical impulses which are received in the output circuit of an electron tube amplifier of a radio receiving system.

Another object of my invention is to pro- Vide an arrangement of armature which is driven by a pair of electromagnets, in the electromagnetic driving system where the armature has a fixed fulcrum adjacent one end thereof and is acted upon by the electromagnets adjacent the extremity thereof, the driving force being taken oif from the extremity of the armature or from a point intermediate the point of application of the electromagnetic driving force and the fulcrum.

A further object of my invention is to pro vide a construction of electromagnetic driver employing a lever principle for the multiplication of effort developed therein, by electromagnetic forces, where the armature may be arranged for the application of magnetic forces at the end opposite the fulcrum of the armature or at a point intermediate the fulcrum and the point at which power for drivr ing a sound reproducer is taken off from the armature.

My invention will be more clearly understood from the specification hereinafter following, by reference to the accompanying drawings, in which:

Figure 1 is a perspective view showing the application of my invention as a driving unit for a phonograph reproducer; Fig.2 is a detailed view showing the extremity of the armature in the electromagnetic driver and the provision for receiving the stylus needle of a phonograph reproducer; Figs. 3

and 4: are theoretical diagrams illustrating the principles of the electromagnetic driver of my invention; Fig. 5 illustrates one form of armature which may be embodied in the electromagnetic driver of my invention; Fig. 6 illustrates a modified form of armature which may be provided in the driving unit of my invention; Fig. 7 is a plan View showing the relationship of the armature and the pole pieces of the driving unit in the electromagnetic sound reproducing device; and Fig. 8 is a partial cross-sectional View showing the assembly of the electromagnetic driving system and the conical diaphragm driven thereby.

I Referrin to the drawings in more detail reference 0 aracter 1 indicates the casing of as the electromagnetic driver, which is use a phonograph attachment and connected through conductors 2 in the output circuit of an audio frequency amplification system which connects to the radio receiving set. My invention will be described particularly with respect to electromagnetic sound repro ducers for radio broadcast reception, but it will be understood that other applications of the principles of my inventionma be made without departing from the spirit of the present application. Reference character 3 designates the extremity of the armature inthe electromagnetic driver receiving in the pocket 3, the stylus needle 4: of a phonograph sound'box 6. Sound box ii is represented as having a lever 7 which is fulcrumed on the periphery of the sound box casing and operates the stylus holder 5, in which the stylus needle 4 is secured. The phonograph attachment has been shown in a position where it rests adjacent the record turn table of the phonograph with the tone arm 9 and swivel 8 extending from the phonograph sound amplifying horn.

' In Figs. '3 and 4 I have shown diagrams illustrating the physical principles embodied in the electromagnetic driving unit of my invention Where the armature is suspended in the form of a lever which is fulcrumed at F and the vibrating force due to the electromagnetic driving unit applied at l? to produce lateral driving force or pull at W.

The driving forcemay be taken 0 from.

- 21 which is secured at 22 to the the armature at the oint P illustrated in Fig. 1 or at the point 11 Fig. 5 I have illustrated one construction of armature which is used in an electromagnetic driver designed in accordance with my invention and wherein the armature has an enlarged circular portion 12 with an upper extremity 14 and a lower extremity- 11 which is fulcrumed to the member 10 which is secured to one side of the casing 1. The member 10 is circular on one edge thereof and its other edge lies substantially chordal with respect to the first edge. That is to say, the member 10 is in the form of a segment of a circle and supports the armature member. Where the armature member is used for driving a cone as represented in Fig. 8, the extension 14 from the circular portion 12 is relatively short. Where, however, the driver is used as a honograph unit the extension 14 is relative y long and terminates in a head 3 which receives the stylus needle of a phonograph at 3" as illustrated in Fig. 7. The circular portion 12 of the armature member lies adjacent the poles 18 of the electromagnetic driver in casmg l and is subjected to thelateral attrac tion and repulsion. forces thereof.

As illustrated in Fig. 8, the driving mechanism may be applied for actuating a conical or other shape diaphragm 20 through ring armature 11. The circular portion 12 of the armature is attracted or repelled by electromagnets 18 driving the cone for translating electrical vibrations into sound. The electromagnetic driver within casing 1 includes a supporting plate 15 which is screwthreaded at 16 into the casing 1 carrying the permanent magnetic system 19 arranged adjacent the electromagnets 18. The control knob 17 is provided for regulating the gap between the pole pieces of electromagnets 18 and the circular portion 12 of the armature member.

By the construction of electromagnetic driver illustrated I am enabled to use the same electromagnetic mechanism as a driver for either a phonograph unit or a cone by merely changin the shape of the armature member and utilizing the principle of Fig. 3 in the case of a phonograph reproducer, while the principle of Fig. 4 is employed when adaptin the driver to a cone typeof reproducer. That is to say, in the case of a phonograph reproducer the armature is arranged as a lever of the third class, while in a cone type loud speaker the armature is arranged in the form of a lever of the second class. It will be appreciated that the changeability in'the design of the device facilitates manufacture where a certain portion of the units going through a large production program may be diverted as drivers: for phonograph reproducers, while other units ma be utilized as drivers for cone speakers w ere illustrated in Fig. 4.

pair of electromagnets in the change in design is merely the substitution of one construction of armature for another.

While I have described my invention in certain preferred embodiments, I desire that it be understood that modifications may be made and that no limitations upon the invention are intended other than those imposed by the scope of the appended claims.

lVhat I claim and desire to secure by Letters Patent of the United States is as follows 1. In an electromagnetic driver, the combination of a casing, an electromagnetic driving unit arranged within said casing including a pair of electromagnets, a se mental member secured across one side 0 said casing adjacent said electromagnets, an armature fulcrumed on said segmental memher and terminating in a circular portion adjacent said electromagnets, whereby said armature is set into vibration as a lever for converting electrical vibrations into sound.

2. An electromagnetic driver comprising in combination a casing, a pair of electromagnets positioned within said casing, a segmental member mounted on the periphery of said casing adjacent said electromagnets, an armature consisting of a relatively thin strip of material extending in the form of a tongue from said segmental member and having a circular portion thereon situated adjacent said electromagnets, electromagnets actuate said armature by repulsion and attraction forces applied to said circular portion.

'3. An electromagnetic driver comprising in combination a casing, an electromagnetic mechanism positioned within said casing, a pair of electromagnets in said casing, a segmental member secured to' one side of said casing, an armature in the form of a strip fulcrumed on said segmental member and extending axially of said electromagnets said strip being enlarged into a substantially circular portion immediatelv adjacent said electromagnets, whereby sai armature may be driven by said electromagnets for con verting electrical vibrations into sound.

4. An electromagnetic driver comprising in combination a casing, an electromagnetic mechanism positioned within said casing, a

said casing, a segmental member secured to one side of said casing, an armature in the form of'a relatively narrow magnetic strip fulcrumed centrally of said ing an enlarged circular central portion lying immediately adjacent said electromagnets whereby repulsion and attraction forces are imparted to said magnetic strip by said electromagnetic driver for converting electrical vibrations into sound.

5. An -electromagnetic driver comprisingin combination a casing, an electromagnetic segmental member and havwhereby said mechanism positioned within said casing, a pair of electromagnets in said casing, a seg mental member secured to one side of said casing, an armature in the form of a tongue. fulcrumed centrally of said segmental member and extending over saide'lectromagnets with the portion of said tongue which lies directly adjacent said electromagnets' enlarged to substantially cover said electromagnets whereby repulsion and attraction 0 forcesmay be applied to said armature by said electromagnets for translating electrical vibrations into sound.

- In testimony whereof I aflix my signature.

RALPH L. BROWN. 

